<p>Numerous studies have investigated the application of copper slag in concrete mixes for traditional construction. However, there is a notable gap in comprehensive research on its potential for three-dimensional concrete printing. This research aims to address this gap by (i) developing concrete mixes using copper slag for 3D printing in the first phase. A total of 37 printing trials are conducted with varying water-to-binder ratios, aggregate-to-binder ratios, and steel fiber dosages to finalize the mix; (ii) in the second phase, a total of nine 3D printable mixes are finalized where the a) fine aggregate in the 3D printable control mix (silica sand) is replaced with copper slag at substitution levels of 0, 25, 50, 75, and 100% and b) steel fiber dosages with two different aspect ratios (29 and 48) and fiber dosages of 1% and 2% are incorporated to characterize fresh density, flowability, compressive and split strength; (iii) in the third phase the static yield stress, dynamic yield stress, and viscosity recovery of are measured at rest times of 10, 20, and 30&#xa0;min using constant shear rate tests, flow curve tests, and three-interval thixotropy tests (iv) finally, energy consumption, CO₂ emissions, cost analysis, and life cycle inventory analysis are evaluated. The findings demonstrate that copper slag exhibits superior buildability and printability properties compared to silica sand. The research shows that up to 100% of the fine aggregate in 3D-printable concrete mixtures can be effectively replaced with copper slag without compromising the material’s strength or printing performance. </p>